WD40 repeat and FYVE domain containing 3 is essential for cardiac development.

Aims: WD40 repeat and FYVE domain containing 3 (WDFY3) is an adaptor protein involved in selective degradation of protein aggregates by autophagy. Recent studies have revealed that Wdfy3 is critical in the regulation of brain development and osteoclastogenesis in vivo. However, the function of Wdfy3 in cardiac development remains completely unknown. In this study, we explore the role of Wdfy3 in cardiac morphogenesis using Wdfy3-deficient mice.

Methods And Results: Wdfy3 was expressed in the developing heart in mice and peaked at embryonic day 12.5 (E12.5). Loss of Wdfy3 in mice led to embryonic and neonatal lethality. Wdfy3-deficient mice displayed various congenital heart defects including membranous ventricular septal defect (VSD), aortic overriding (AO), double outlet right ventricle (DORV), thinning of ventricular wall, ventricular dilation, and disorganized ventricular trabeculation at E14.5. Cell proliferation was reduced in the hearts from Wdfy3-deficient mice at E12.5 and E14.5, which was associated with enhanced p21 expression. Cardiomyocyte differentiation was diminished as demonstrated by reduced Myh6 and MLC2v in Wdfy3-deficient mice at E14.5. In addition, Nkx2-5 and Mef2c, two cardiac transcription factors regulating cardiomyocyte differentiation, were decreased in Wdfy3-deficient mice at E14.5. Apoptotic cell death remained unaltered. These data suggest that reduced cell proliferation and cardiomyocyte differentiation contribute to cardiac defects in Wdfy3-deficient mice. Mechanistically, loss of Wdfy3 led to a reduction in protein levels of Notch 1 intracellular domain and its downstream targets Hes1 and Hey1, which was accompanied with enhanced full-length Notch1 protein levels. In vitro luciferase assay showed that Wdfy3 deficiency induced activity of p21 promoter, while diminished activity of Hes1 promoter through modulation of Notch1 signalling. Moreover, Wdfy3 was co-localized with Notch1 in primary embryonic cardiomyocytes. Endogenous Wdfy3 physically interacted with full-length Notch1 in the developing heart. These results suggest that Notch1 signalling is perturbed in the hearts from Wdfy3-deficient mice. No alteration of autophagy was detected in the hearts from Wdfy3-deficient mice.

Conclusion: Taken together, our data suggest that Wdfy3 plays an essential role in cardiac development, which may be mediated by modulation of Notch1 signalling.